Synopsis The exercise of police functions in the Police Agent of Public Security, linked to forensic practice, and currently in the tax inspection, made possible the development of this report on the proposed theme, which comprises the various materials referenced there and somehow comprehensive, which are considered important and relevant as a result of professional experience, given the need that exists in the collection of legal form of the means of (obtaining) evidence in criminal proceedings and their probative value, given the practice of the types of illicit criminal and tax offenses, not only by the difficulties arising in this achievement by the criminal Police Bodies (OPC), but also by the various departments of tax Inspection (IT) of the Tax and Customs Authority (TA) and which should be examined. The first part is made reference to own organic and statutory regime of the Public Security Police and a study on police action earlier in the beginning of the criminal process, ie, the socalled precautionary measures and police. In the second part means up approach of (obtaining) proves used in the exercise of these functions, constants in the Portuguese legal system, particularly with regard to examinations, the magazine and the seizures and call into play some doctrinal differences and also jurisprudential , jurisprudence which is exclusively addressed in the fourth part. Here covers, above all the complexity and validity in the acquisition of the means of (obtaining) evidence at the police activity. The third part of the study, closely linked to the second focuses on the evidence. One approach to the issue of probative value for recognition based research and investigation of people and later at the trial stage, the indirect testimony, also ending in reference jurisprudential vision for the probative value of the statements of the accused to the police authorities, divergent from those statements made in court within the same process. Likewise are referred to the relevant court decisions in this area and their evolution on some issues, in the fourth part of the study. In the fifth and final part, proceeds to the media approach of (obtaining) the evidence to be of relevance in the context of policing and tax inspection procedure, including the precautionary measures and police on the one hand, and the means test used in the procedure of Tax Inspection, including the documentary and testimonial evidence, on the other. This report focuses also, albeit briefly, about getting the digital proof, an issue that has proved to be current, since the technological development in general and the creation of the IT systems of the tax authorities in their relationship with the taxpayers, in particular, has lead to the emergence of new “modus operandi” for certain typified, specifically with regard to the issuance of fake invoices via computer applications and billing certificate programs.